In co-pending U.S. patent application Ser. No. 665,657, filed 10/29/84, now allowed, a liquid-propellant management system was described in which liquid propellant is controllably expelled by means of pressurant gas from a rigid-walled storage tank to the thrusters of a space vehicle in such a way that substantially gas-free liquid propellant is delivered to the thrusters without interruption during accelerations involving rapid changes in speed and/or direction.
The liquid-propellant management system described in U.S. patent application Ser. No. 665,657 comprises a hollow storage tank, a hollow trap of lenticular configuration (i.e., of clam-shell shape, with a spherical shape being the limiting case), and a trap liner. The trap is positioned inside the storage tank at a polar region thereof (i.e., so as to occupy an end portion of an elongate tank, or considerably less than a hemispheric portion of a spherical tank), and the trap liner is positioned inside the trap.
The storage tank of the system described in U.S. patent application Ser. No. 665,657 has a first opening connectable to a so-called "pressurant and vent" line for pressurant gas, and a second opening connectable to a so-called "fill, drain and feed" line for liquid propellant. The trap is secured within the storage tank in the vicinity of the "fill, drain and feed" line, and an exit port of the trap is aligned with the second opening in the tank so as to communicate with the "fill, drain and feed" line. The liner is secured to the interior wall of the trap circumjacent a porous inlet window, and is configured generally in conformity with the contour of the interior wall of the trap. Except where the liner is secured circumjacent the inlet window, the liner is spaced apart from the interior wall of the trap to define a volume between the liner and the trap. The inlet window of the trap admits liquid propellant from the storage tank into the interior of the liner. The liner has a plurality of porous outlet windows, which permit flow of liquid propellant from the interior of the liner into the volume between the exterior wall of the liner and the interior wall of the trap. Liquid propellant is then expelled from the volume between the liner and the trap via the exit port of the trap to the "fill, drain and feed" line for delivery as needed to the thrusters of the space vehicle.
The inlet window of the trap and the outlet windows of the liner of the liquid-propellant management system of U.S. patent application Ser. No. 665,657 have capillary pores, which permit liquid propellant that comes into contact with the windows to pass therethrough. The pores are dimensioned so that, when liquid propellant stored in the storage tank and/or in the trap is not in contact with the windows (as may occur during accelerations with less than a full storage tank), a film of liquid propellant is maintained across each pore by surface tension after the windows have been wetted by the liquid propellant. The films of liquid propellant across the pores of the inlet window of the trap act as a barrier to the entry of pressurant gas from the interior of the tank outside the trap into the interior of the liner inside the trap. Similarly, the films of liquid propellant across the pores of the liner windows prevent any pressurant gas that may be inside the liner from entering into the volume between the liner and the trap.